Android code to copy file, directory, and clear directory.

copy_file_dir_clear_dir.java

		/**
		 * Copy file from {@code src} to  {@code dest}.
		 *
		 * @param src
		 * 		Source.
		 * @param dest
		 * 		Destination.
		 *
		 * @throws IOException
		 */
		private void copyFile(File src, File dest) throws IOException {
			InputStream in = new FileInputStream(src);
			OutputStream out = new FileOutputStream(dest);

			// Transfer bytes from in to out
			byte[] buf = new byte[1024];
			int len;
			while ((len = in.read(buf)) > 0) {
				out.write(buf, 0, len);
			}
			in.close();
			out.close();
		}
		
		
		/**
		 * Copy dir from {@code src} tor {@code dest}.
		 *
		 * @param src
		 * 		The target we will write for downloading data.
		 * @param dest
		 * 		Backup location.
		 */
		private void copyDir(File src, File dest) {
			if (src == null || !src.exists()) {
				Log.w(TAG, "Can't do copyDir because src doesn't exist or even null by passed.");
			} else {
				if (!src.isFile()) {
					if (!dest.exists()) {
						dest.mkdir();
					}
				} else {
					if (!dest.exists()) {
						try {
							copyFile(src, dest);
						} catch (IOException e) {
							e.printStackTrace();
						}
					}
				}
				if (src.isDirectory()) {
					File[] files = src.listFiles();
					for (File file : files) {
						//Do again for sub-dir or files.
						copyDir(file, new File(dest, file.getName()));
					}
				}
			}
		}
		
		
		/**
		 * Remove the directory.
		 *
		 * @param dir
		 * 		The location to delete.
		 */
		private void clearDir(File dir) {
			File[] files = dir.listFiles();
			for (File file : files) {
				if (file.isDirectory()) {
					clearDir(file);
				} else {
					file.delete();
				}
			}
			dir.delete();
		}